The invention relates to a clamp used in an external bone fixation device. More particularly, the invention relates to a clamp for coupling a longitudinal support and a bone fixation device such as a Schanz screw or any other suitable bone fastener.
Open fractures of the 2nd and 3rd degrees, infection pseudoarthroses and corrective interventions for axial deviations and length differences are among the most important indications for external fixation devices. A number of clamps for use in such external fixation devices are already known, however prior art clamps have the drawback of requiring exceedingly accurate manufacture and concomitantly high cost.
There exists a need for an improved clamp that has a simple design and can be manufactured with relatively low tolerances, yet still permits the desired component fixation for palliative effect.
There further exists a need for an improved clamp with a design that is free of tight tolerances, and thus can be used with a wide range of external fixation devices. Such a versatile clamp can offer ease of high production runs and simplified logistics, thereby meeting the needs of developing and threshold countries. Despite the simple, manufacturing-friendly design, the clamp should offer many degrees of freedom, similar to conventional, more complex and costly clamps of the prior art.
Additionally, there is a need for an improved clamp designed with features having generous tolerances so that the longitudinal support may be bent to fit the anatomy. Such a design is useful, for example, when tending to pelvic fractures, which currently are typically treated only with pre-bent longitudinal supports or with several longitudinal supports mutually connected by articulating jaws.
The present invention provides a clamp that is capable of providing these improvements.
The present invention is related to a clamp for an external bone fixation device, and includes a body having first, second and third boreholes extending therein, a longitudinal support, a coupling member for coupling to a bone fastener, and a tightening component. The first borehole extends along a first longitudinal axis and is configured and dimensioned for receiving the longitudinal support, while the second borehole extends along a second longitudinal axis and is configured and dimensioned for receiving the coupling member. The third borehole extends along a third longitudinal axis and is configured and dimensioned for receiving the tightening component. The first longitudinal axis is oriented at an angle with respect to the second longitudinal axis, and the third longitudinal axis is substantially perpendicular to both the first and second longitudinal axes. The third borehole extends from a surface of the block to intersect the second borehole, and the first and second boreholes at least partially intersect each other. In addition, the longitudinal support in the first borehole and the coupling member in the second borehole are simultaneously fixed in position when the tightening component bears against the member and the member bears against the longitudinal support.
In the preferred embodiment, the third borehole is threaded and only extends to the intersection with the second borehole, with the tightening component also being correspondingly threaded to engage the threaded borehole. The coupling member includes a first end and a second end, and a through hole proximate the first end for receiving a bone fastener. Also, the first and second boreholes are substantially perpendicular to each other. The coupling member may further include a threaded portion proximate the second end, and a nut may be provided for threadably engaging the threaded portion of the coupling member. The body may have a rectangular form with six faces, each face having smooth or beveled edges. The body may instead have a parallelepiped shape. The member may be generally cylindrical and have a member diameter, while the second bore may have a second diameter, with the member diameter being smaller than the second diameter to permit the member to freely move within the second bore. Furthermore, the through hole may have a hole diameter, the bone fastener may have a fastener diameter, and the hole diameter may be about the same as the fastener diameter.
In the preferred embodiment, the tightening component is formed of a first material and the body is formed of a second material, with the first material being harder than the second material. The first material may be steel while the second material may be aluminum. In addition, the longitudinal support may be formed of a third material, with the first material being harder that the third material.
The present invention also is related to a clamp for simultaneously fixing the positions of a longitudinal member and a bone fastener with respect to each other. The clamp includes a parallelepiped body with two unthreaded holes and one threaded hole extending therein, a member for coupling to a bone fastener, a nut for coupling to the member, and a threaded tightening component. The threaded tightening component threadably engages the threaded hole, and when the threaded tightening component bears against the member, the member can bear against the longitudinal member.
The invention further relates to a clamp comprising a parallelipipedic basic body and a tension bolt. The basic body is fitted with a first and continuous borehole to receive a longitudinal support, and also is fitted with a second and continuous borehole disposed perpendicular to the first borehole and partly crossing it. The tension bolt may have a head, and can be inserted by its free end into the second borehole, the head forming a stop against the basic body. Proximate its free end, the tension bolt is threaded, the threads provided for engaging a nut that forms a stop against the basic body. The tension bolt may include an unthreaded shank part located between the threaded portion and the head, and in a preferred embodiment also is fitted with a transverse borehole in the unthreaded shank part proximate the head to receive a bone fixation device. The transverse borehole can be moved by the nut into the proximity of the second borehole, with a bone fixation device being displaceable in this process to come to rest against the basic body. The basic body further is fitted with a threaded borehole running perpendicular to both the first and second continuous bore holes, terminating in the second borehole and receiving a fixation screw. In a preferred embodiment, the diameter of the tension bolt is smaller than the diameter of the second borehole, so that the tension bolt can be moved by the fixation screw into the zone of the second borehole to tangentially rest against the longitudinal support.
In one embodiment, the basic body is made of aluminum, and the bone fixation device is preferably made of a material that is harder than that of the basic body. The tension bolt is preferably made of steel, and also is preferably made of a material harder than that of the basic body. In addition, the longitudinal support is preferably made of a softer material than that of the tension bolt.
Advantageously, in a preferred embodiment, the clamp body is only used to receive the two tightening elements (one for the longitudinal support and the other for the bone screw). Furthermore, the position of the tightening element for the bone screw also is fixed when the longitudinal support is fixed. The clamp may permit bone screws of different diameters to be tightened. Also, the clamp design is size-independentxe2x80x94that is, the same clamp design is applicable to fractures of thighs, lower arms and fingers.